Electronic countermeasures (ECM) are a subsection of electronic warfare (EW) which includes any sort of electrical or electronic device designed to deceive radar, sonar, or other detection systems. Electronic countermeasures may be used both offensively and defensively in any method to deny targeting information to an enemy. For example, ECM may cause the detecting radar system to falsely “identify” many separate targets or make the real target appear and disappear or move about randomly. ECM is used effectively to protect aircraft from guided missiles. Most air forces use them to protect their aircraft from attack.
Offensive ECM often takes the form of jamming. Defensive ECM includes using chaff and flares against incoming missiles, as well as soids (floating flares that are effective only in the terminal phase of missiles with infrared signature seeker heads), blip enhancement and jamming of missile terminal homers. When employed effectively ECM can keep aircraft from being tracked by search radars, surface-to-air missiles and air-to-air missiles.
Electronic counter-countermeasures (ECCM) describe a variety of practices which attempt to reduce or eliminate the effect of ECM on electronic sensors aboard vehicles, ships and aircraft and weapons such as missiles. ECCM is also referred to as Electronic Protective Measures (EPM), chiefly in Europe.
ECM is practiced by nearly all military units—land, sea or air. Aircraft are the primary weapons in the ECM battle because they can “see” a larger patch of earth than a sea or land-based unit. When employed effectively ECM can keep aircraft from being tracked by search radars, surface-to-air missiles and air-to-air missiles.
Modern radar-based threat systems with advanced Electronic Counter-Counter Measures capabilities are immune to existing on-board ECM techniques and pose a real threat to airborne platforms. Several methods for off-board protecting means had been suggested in the past. U.S. Pat. No. 5,333,814 describes a towed body aimed to intercept or collide with incoming threats but without any ECM capability. U.S. Pat. No. 6,492,931 describes an expendable decoy that operates off-board but is dependent on the equipment residing in the protected platform. This decoy is not a stand-alone jammer that can work autonomously against multiple targets and it poses major limitations on the flight envelope of the platform after the launching. Other towed decoy jammers are also known to act in close dependence with the protected platform, both electrically and mechanically. These types of decoy also limit the aircraft maneuvers and lowers the efficiency of other protective measures.
U.S. Pat. No. 6,429,800 deals with a true off-board expendable jammer. However, this decoy has no “receive” capability and/or any independent recognition of the enemy threats. It has no Digital Radio Frequency Memory (DRFM)-based equipment that can optimize the deceiving technique, nor any updating mechanism. It has no mechanical and aerodynamical detailed design. The spatial coverage and the frequency coverage are not explicitly described, thus the efficiency against multiple type threats arising from all directions is not proved.